Re: [ftpext] Discouraging use of TCP "urgent data"

Fernando Gont <fernando@gont.com.ar> Wed, 22 September 2010 13:59 UTC

Return-Path: <fernando.gont.netbook.win@gmail.com>
X-Original-To: ftpext@core3.amsl.com
Delivered-To: ftpext@core3.amsl.com
Received: from localhost (localhost [127.0.0.1]) by core3.amsl.com (Postfix) with ESMTP id 43A9A3A6955 for <ftpext@core3.amsl.com>; Wed, 22 Sep 2010 06:59:39 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.438
X-Spam-Level:
X-Spam-Status: No, score=-2.438 tagged_above=-999 required=5 tests=[AWL=0.161, BAYES_00=-2.599]
Received: from mail.ietf.org ([64.170.98.32]) by localhost (core3.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id TK2BsID5E3NT for <ftpext@core3.amsl.com>; Wed, 22 Sep 2010 06:59:38 -0700 (PDT)
Received: from mail-gw0-f66.google.com (mail-gw0-f66.google.com [74.125.83.66]) by core3.amsl.com (Postfix) with ESMTP id 5A5D43A6AE5 for <ftpext@ietf.org>; Wed, 22 Sep 2010 06:59:38 -0700 (PDT)
Received: by gwb11 with SMTP id 11so106871gwb.1 for <ftpext@ietf.org>; Wed, 22 Sep 2010 07:00:05 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:sender:message-id:date:from :user-agent:mime-version:to:cc:subject:references:in-reply-to :x-enigmail-version:openpgp:content-type:content-transfer-encoding; bh=epu2g41mp2HrKi+DXdqZDUb3DeVwx+iympNVBiVRqoc=; b=L5skYjjVcaKKpie2kG+/zLkA4jGGNGHvSKSc2/uXot+A/RJRNA1i7GXI/RutYSnsVS 6mx7augqtS4XcwXGIgm+IEwmVyFpAJFdCF1RYjbnYMt9TWuRnN987htllYydrNnOOGb1 yP7u364u1R8LGFIa2G2nZctPUuAyBFNrRtcr4=
DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:openpgp:content-type :content-transfer-encoding; b=i6kwBza2Si72hoLjPNV5LN/vahBIz+kOVpvwLhSd6d+afppH52359ZcgvPpAxWZNvv QSAPAeZxL47AZIsbyJzzMpHmrZk7Ao5nzGmCXjKedUaukf20VCfh8GqylSEjyebewTF/ ku/mlpU0qKNkBJKCYwR66AStSz/thZhvj9n6k=
Received: by 10.150.95.19 with SMTP id s19mr1094266ybb.143.1285164004725; Wed, 22 Sep 2010 07:00:04 -0700 (PDT)
Received: from [192.168.0.133] (61-128-17-190.fibertel.com.ar [190.17.128.61]) by mx.google.com with ESMTPS id i4sm11422924ybd.15.2010.09.22.07.00.01 (version=TLSv1/SSLv3 cipher=RC4-MD5); Wed, 22 Sep 2010 07:00:03 -0700 (PDT)
Sender: Fernando Gont <fernando.gont.netbook.win@gmail.com>
Message-ID: <4C9A056C.9010808@gont.com.ar>
Date: Wed, 22 Sep 2010 10:32:28 -0300
From: Fernando Gont <fernando@gont.com.ar>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.8) Gecko/20100802 Thunderbird/3.1.2
MIME-Version: 1.0
To: "William F. Maton" <wmaton@ottix.net>
References: <4C98B731.2030802@isode.com> <Pine.LNX.4.64.1009211253500.29844@iskra.ottix.net>
In-Reply-To: <Pine.LNX.4.64.1009211253500.29844@iskra.ottix.net>
X-Enigmail-Version: 1.1.1
OpenPGP: id=D076FFF1
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: Alexey Melnikov <alexey.melnikov@isode.com>, ftpext@ietf.org
Subject: Re: [ftpext] Discouraging use of TCP "urgent data"
X-BeenThere: ftpext@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: <ftpext.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/listinfo/ftpext>, <mailto:ftpext-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/ftpext>
List-Post: <mailto:ftpext@ietf.org>
List-Help: <mailto:ftpext-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ftpext>, <mailto:ftpext-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 22 Sep 2010 13:59:39 -0000

Hi, William,

>> This is somewhat related to FTP: there is currently a document in IESG
>> review talking about deprecation (or strong discouragement) of use of
>> TCP urgent data:
>>
>> <https://datatracker.ietf.org/doc/draft-ietf-tcpm-urgent-data/>
>>
>> I would like to ask people to review this and tell me how this affect
>> FTP.
> 
> Just taking a quick peek, looks like it isn't relevant to RFC 4217 at
> least, but as section 14 points out, 'FTP uses the Telnet Interrupt
> Process and Data Mark commands in conjunction with Urgent data to
> preface two commands: ABOR (Abort Transfer) and STAT (Status request).'
> 
> If 'urgent data' isn't recommended for new apps, then FTP is ...... ?

FTP can get away with its use of urgent data because it's a legacy app
;-) . However, it should set SO_OOBINLINE (or the like) such that the
urgent data is delivered inline.

Please note that Cisco Pix (and probably others) clear the URG bit by
default.... so be prepared for the urgent indications to be unreliable...

Thanks!

Kind regards,
-- 
Fernando Gont
e-mail: fernando@gont.com.ar || fgont@acm.org
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1